Summary
The UpdateKernel which is used by update.php to run the update hooks now removes services and aliases with unmet dependencies from its dependency injection container.
Before
Before this change module developers had to use setter injection or ignoring missing dependencies and guarding their services for those cases because update hooks could not be run due to the container throwing an exception.
After
The changes introduced with #2863986: Allow updating modules with new service dependencies allow installed modules services to depend on yet uninstalled module services as long as the existing module installs the new module in an update hook, and that's because the normal service container will throw an exception when there are unmet dependencies.
Please note those services with unmet dependencies will not be available during update hooks.
